Abstract

We demonstrate CoFeB/MgO/CoFeB sensors with field noise level below magnetic noise-sensitivity scaling limit and significant reduction of 1/f noise corner frequency. The sensors show more than three orders of magnitude reduction of voltage noise and drop of the corner frequency from 100 kHz to 1 kHz. We achieved this by changing the sensors field sensitivity from 127 (V/T) to 2.7 (V/T) via perpendicular anisotropy-induced field sensitivity modulation. The reduction of the field noise beyond the scaling limit presents sensors for specific field sensitivity. The field sensitivity modulation in our sensors enables magnetic noise reduction that improves field noise (detectivity) and shifts magnetic 1/f corner to lower frequency. The shift of 1/f corner frequency together with the magnetic noise reduction indicates importance of anisotropy-induced sensitivity modulation in reduction of low frequency magnetization fluctuations in CoFeB/MgO/CoFeB sensors.

This work was supported by the Polish National Science Centre Grant DEC-2012/04/M/ST7/00799. M.D. acknowledges financial support of the Polish Ministry of Science and Higher Education 0148/DIA/2013/42.